Make sure you've installed the latest Xcode + tools before proceeding; check App Store for updates. Be sure to accept the Xcode License before proceeding!
Make sure you have the **readline** lib installed:
*`brew --prefix readline`
* if you get Error: No available formula with the name "readline", install readline:
*`brew install readline`
*`brew link --force readline` You'll need to use `--force` to make it work.
*`vi ~/.rvm/user/db` and add the following: `ruby_configure_flags=--with-readline-dir=/usr/local/opt/readline`
Reinstall Ruby, with a rebuild of sources:
*`rvm reinstall <your_ruby_version>` This command removes the specified version's ruby binaries and libs, and rebuilds from source code on your system, with the latest macOS headers and libs.
*`rvm reinstall <your_ruby_version> --gems` This command repro's the same steps as above, but it removes the gems first as well. The next time you run bundle install the gems will be downloaded and rebuilt against your latest ruby. This can help resolve other potential issues with gems after rebuilding ruby on macOS.
* Change the specified version (2.5.1 in my case) to match your needs.
* **I ended up using the second syntax for a completely fresh start.**
_Gotchas:_ If you're in the project directory running a terminal window when finished this process, You'll had to `cd ..` up a level and then `cd project-folder` back into the project so that RVM would reactivate your gemset.